diff --git a/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractCreateMethodsStage.java b/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractCreateMethodsStage.java
index f673a89..da3b968 100644
--- a/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractCreateMethodsStage.java
+++ b/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractCreateMethodsStage.java
@@ -49,6 +49,7 @@ protected void createPropertyMethods(JavaSource<?> javaEntity, PropertyModelWith
             createAddMethod(javaEntity, collectionPropertyWithOrigin);
             createClearMethod(javaEntity, collectionPropertyWithOrigin);
             createRemoveMethod(javaEntity, collectionPropertyWithOrigin);
+            createInsertMethod(javaEntity, collectionPropertyWithOrigin);
         } else if (isPrimitive(property) || isPrimitiveList(property) || isPrimitiveMap(property)) {
             createGetter(javaEntity, propertyWithOrigin);
             createSetter(javaEntity, propertyWithOrigin);
@@ -62,6 +63,7 @@ protected void createPropertyMethods(JavaSource<?> javaEntity, PropertyModelWith
             createAddMethod(javaEntity, propertyWithOrigin);
             createClearMethod(javaEntity, propertyWithOrigin);
             createRemoveMethod(javaEntity, propertyWithOrigin);
+            createInsertMethod(javaEntity, propertyWithOrigin);
         } else if (isUnion(property)) {
             createGetter(javaEntity, propertyWithOrigin);
             createSetter(javaEntity, propertyWithOrigin);
@@ -171,7 +173,7 @@ protected void createFactoryMethod(JavaSource<?> javaEntity, PropertyType proper
 
     /**
      * Creates an "add" method for the given property.  The type of the property must be a
-     * list of entities.  The add method would accept a single entity and add it to the list.
+     * collection of entities.  The add method will accept a single entity and add it to the collection.
      * @param javaEntity
      * @param propertyWithOrigin
      */
@@ -219,7 +221,7 @@ protected void createAddMethod(JavaSource<?> javaEntity, PropertyModelWithOrigin
 
     /**
      * Creates a "clear" method for the given property.  The type of the property must be a
-     * list of entities.  The clear method will remove all items from the list.
+     * collection of entities.  The clear method will remove all items from the collection.
      * @param javaEntity
      * @param propertyWithOrigin
      */
@@ -237,8 +239,8 @@ protected void createClearMethod(JavaSource<?> javaEntity, PropertyModelWithOrig
 
     /**
      * Creates a "remove" method for the given property.  The type of the property must be a
-     * list of entities.  The remove method will remove one item from the list.
-     * @param entity
+     * collection of entities.  The remove method will remove one item from the collection.
+     * @param javaEntity
      * @param propertyWithOrigin
      */
     protected void createRemoveMethod(JavaSource<?> javaEntity, PropertyModelWithOrigin propertyWithOrigin) {
@@ -266,6 +268,56 @@ protected void createRemoveMethod(JavaSource<?> javaEntity, PropertyModelWithOri
     }
     abstract protected void createRemoveMethodBody(PropertyModel property, MethodSource<?> method);
 
+    /**
+     * Creates an "insert" method for the given property.  The type of the property must be a
+     * collection of entities.  The insert method will add one item to the collection at
+     * a specific index (if possible).
+     * @param javaEntity
+     * @param propertyWithOrigin
+     */
+    protected void createInsertMethod(JavaSource<?> javaEntity, PropertyModelWithOrigin propertyWithOrigin) {
+        PropertyModel property = propertyWithOrigin.getProperty();
+
+        String _package = propertyWithOrigin.getOrigin().getNamespace().fullName();
+        PropertyType type = property.getType().getNested().iterator().next();
+        String methodName = insertMethodName(singularize(property.getName()));
+        MethodSource<?> method;
+
+        if (type.isEntityType()) {
+            JavaInterfaceSource entityType = resolveJavaEntityType(_package, type);
+            if (entityType == null) {
+                error("Could not resolve entity type: " + _package + "::" + type);
+                return;
+            }
+
+            javaEntity.addImport(entityType);
+
+            method = ((MethodHolderSource<?>) javaEntity).addMethod().setPublic().setName(methodName).setReturnTypeVoid();
+            addAnnotations(method);
+            if (property.getType().isMap()) {
+                method.addParameter("String", "name");
+            }
+            method.addParameter(entityType.getName(), "value");
+        } else if (type.isPrimitiveType()) {
+            Class<?> primitiveType = primitiveTypeToClass(type);
+            javaEntity.addImport(primitiveType);
+
+            method = ((MethodHolderSource<?>) javaEntity).addMethod().setPublic().setName(methodName).setReturnTypeVoid();
+            addAnnotations(method);
+            if (property.getType().isMap()) {
+                method.addParameter("String", "name");
+            }
+            method.addParameter(primitiveType.getSimpleName(), "value");
+        } else {
+            warn("Type not supported for 'add' method: " + methodName + " with type: " + property.getType());
+            return;
+        }
+        method.addParameter("int", "atIndex");
+
+        createInsertMethodBody(javaEntity, property, method);
+    }
+    abstract protected void createInsertMethodBody(JavaSource<?> javaEntity, PropertyModel property, MethodSource<?> method);
+
     /**
      * Create factory methods for any entity types in the union.  If the union is, for example, "boolean|string"
      * then this will do nothing.  But if the union is "Widget|string" then a factory method for Widgets will
diff --git a/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractJavaStage.java b/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractJavaStage.java
index 076364b..227df8a 100644
--- a/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractJavaStage.java
+++ b/generator/src/main/java/io/apicurio/umg/pipe/java/AbstractJavaStage.java
@@ -177,6 +177,10 @@ protected String getRootNodeEntityClassFQN() {
         return getState().getConfig().getRootNamespace() + ".RootNodeImpl";
     }
 
+    protected String getDataModelUtilFQCN() {
+        return getState().getConfig().getRootNamespace() + ".util.DataModelUtil";
+    }
+
     protected String getParentPropertyTypeEnumFQN() {
         return getState().getConfig().getRootNamespace() + ".ParentPropertyType";
     }
@@ -233,6 +237,18 @@ protected String addMethodName(String name) {
         return "add" + StringUtils.capitalize(name);
     }
 
+    protected String insertMethodName(EntityModel entityModel) {
+        return insertMethodName(entityModel.getName());
+    }
+
+    protected String insertMethodName(PropertyModel propertyModel) {
+        return insertMethodName(propertyModel.getName());
+    }
+
+    protected String insertMethodName(String name) {
+        return "insert" + StringUtils.capitalize(name);
+    }
+
     protected String clearMethodName(EntityModel entityModel) {
         return clearMethodName(entityModel.getName());
     }
diff --git a/generator/src/main/java/io/apicurio/umg/pipe/java/CreateImplMethodsStage.java b/generator/src/main/java/io/apicurio/umg/pipe/java/CreateImplMethodsStage.java
index 67f86db..cef9187 100644
--- a/generator/src/main/java/io/apicurio/umg/pipe/java/CreateImplMethodsStage.java
+++ b/generator/src/main/java/io/apicurio/umg/pipe/java/CreateImplMethodsStage.java
@@ -151,6 +151,34 @@ protected void createMappedNodeMethods(JavaSource<?> javaEntity, PropertyModelWi
             method.setBody(body.toString());
         }
 
+        // void insertItem(String name, T item, int atIndex)
+        {
+            MethodSource<?> method = ((MethodHolderSource<?>) javaEntity).addMethod().setName("insertItem").setPublic().setReturnTypeVoid();
+            method.addAnnotation(Override.class);
+            method.addParameter("String", "name");
+            method.addParameter(mappedNodeType, "item");
+            method.addParameter("int", "atIndex");
+
+            JavaClassSource dataModelUtilSource = getState().getJavaIndex().lookupClass(getDataModelUtilFQCN());
+            javaEntity.addImport(dataModelUtilSource);
+
+            BodyBuilder body = new BodyBuilder();
+            body.append("this._items = DataModelUtil.insertMapEntry(this._items, name, item, atIndex);");
+            if (isEntity(property)) {
+                JavaEnumSource parentPropertyTypeSource = getState().getJavaIndex().lookupEnum(getParentPropertyTypeEnumFQN());
+                javaEntity.addImport(parentPropertyTypeSource);
+                JavaClassSource nodeImplSource = getState().getJavaIndex().lookupClass(getNodeEntityClassFQN());
+                javaEntity.addImport(nodeImplSource);
+
+                body.append("if (item != null) {");
+                body.append("    ((NodeImpl) item)._setParentPropertyName(null);");
+                body.append("    ((NodeImpl) item)._setParentPropertyType(ParentPropertyType.map);");
+                body.append("    ((NodeImpl) item)._setMapPropertyName(name);");
+                body.append("}");
+            }
+            method.setBody(body.toString());
+        }
+
         // T removeItem(String name)
         {
             MethodSource<?> method = ((MethodHolderSource<?>) javaEntity).addMethod().setName("removeItem").setPublic();
@@ -333,6 +361,69 @@ protected void createRemoveMethodBody(PropertyModel property, MethodSource<?> me
         method.setBody(body.toString());
     }
 
+    @Override
+    protected void createInsertMethodBody(JavaSource<?> javaEntity, PropertyModel property, MethodSource<?> method) {
+        PropertyType type = property.getType().getNested().iterator().next();
+        String fieldName = getFieldName(property);
+        String propertyName = property.getName();
+
+        BodyBuilder body = new BodyBuilder();
+        body.addContext("fieldName", fieldName);
+        body.addContext("propertyName", propertyName);
+
+        if (type.isEntityType() || type.isPrimitiveType()) {
+            if (property.getType().isMap()) {
+                JavaClassSource dataModelUtilSource = getState().getJavaIndex().lookupClass(getDataModelUtilFQCN());
+                javaEntity.addImport(dataModelUtilSource);
+                javaEntity.addImport(LinkedHashMap.class);
+
+                body.append("if (this.${fieldName} == null) {");
+                body.append("    this.${fieldName} = new LinkedHashMap<>();");
+                body.append("    this.${fieldName}.put(name, value);");
+                body.append("} else {");
+                body.append("    this.${fieldName} = DataModelUtil.insertMapEntry(this.${fieldName}, name, value, atIndex);");
+                body.append("}");
+
+                if (type.isEntityType()) {
+                    JavaEnumSource parentPropertyTypeSource = getState().getJavaIndex().lookupEnum(getParentPropertyTypeEnumFQN());
+                    javaEntity.addImport(parentPropertyTypeSource);
+                    JavaClassSource nodeImplSource = getState().getJavaIndex().lookupClass(getNodeEntityClassFQN());
+                    javaEntity.addImport(nodeImplSource);
+
+                    body.append("if (value != null) {");
+                    body.append("    ((NodeImpl) value)._setParentPropertyName(\"${propertyName}\");");
+                    body.append("    ((NodeImpl) value)._setParentPropertyType(ParentPropertyType.map);");
+                    body.append("    ((NodeImpl) value)._setMapPropertyName(name);");
+                    body.append("}");
+                }
+            } else {
+                JavaClassSource dataModelUtilSource = getState().getJavaIndex().lookupClass(getDataModelUtilFQCN());
+                javaEntity.addImport(dataModelUtilSource);
+                javaEntity.addImport(ArrayList.class);
+
+                body.append("if (this.${fieldName} == null) {");
+                body.append("    this.${fieldName} = new ArrayList<>();");
+                body.append("    this.${fieldName}.add(value);");
+                body.append("} else {");
+                body.append("    this.${fieldName} = DataModelUtil.insertListEntry(this.${fieldName}, value, atIndex);");
+                body.append("}");
+                if (type.isEntityType()) {
+                    JavaEnumSource parentPropertyTypeSource = getState().getJavaIndex().lookupEnum(getParentPropertyTypeEnumFQN());
+                    javaEntity.addImport(parentPropertyTypeSource);
+                    JavaClassSource nodeImplSource = getState().getJavaIndex().lookupClass(getNodeEntityClassFQN());
+                    javaEntity.addImport(nodeImplSource);
+
+                    body.append("if (value != null) {");
+                    body.append("    ((NodeImpl) value)._setParentPropertyName(\"${propertyName}\");");
+                    body.append("    ((NodeImpl) value)._setParentPropertyType(ParentPropertyType.array);");
+                    body.append("}");
+                }
+            }
+        }
+
+        method.setBody(body.toString());
+    }
+
     @Override
     protected void addAnnotations(MethodSource<?> method) {
         method.addAnnotation(Override.class);
diff --git a/generator/src/main/java/io/apicurio/umg/pipe/java/CreateInterfaceMethodsStage.java b/generator/src/main/java/io/apicurio/umg/pipe/java/CreateInterfaceMethodsStage.java
index 9663d44..0da3e70 100644
--- a/generator/src/main/java/io/apicurio/umg/pipe/java/CreateInterfaceMethodsStage.java
+++ b/generator/src/main/java/io/apicurio/umg/pipe/java/CreateInterfaceMethodsStage.java
@@ -131,4 +131,7 @@ protected void createClearMethodBody(PropertyModel property, MethodSource<?> met
     protected void createRemoveMethodBody(PropertyModel property, MethodSource<?> method) {
     }
 
+    @Override
+    protected void createInsertMethodBody(JavaSource<?> javaEntity, PropertyModel property, MethodSource<?> method) {
+    }
 }
diff --git a/generator/src/main/java/io/apicurio/umg/pipe/java/LoadBaseClassesStage.java b/generator/src/main/java/io/apicurio/umg/pipe/java/LoadBaseClassesStage.java
index 7ddaf56..f6b79cc 100644
--- a/generator/src/main/java/io/apicurio/umg/pipe/java/LoadBaseClassesStage.java
+++ b/generator/src/main/java/io/apicurio/umg/pipe/java/LoadBaseClassesStage.java
@@ -30,6 +30,7 @@ protected void doProcess() {
             loadBaseClasses(
                     "io.apicurio.umg.base.NodeImpl",
                     "io.apicurio.umg.base.RootNodeImpl",
+                    "io.apicurio.umg.base.util.DataModelUtil",
                     "io.apicurio.umg.base.util.JsonUtil",
                     "io.apicurio.umg.base.util.ReaderUtil",
                     "io.apicurio.umg.base.util.WriterUtil",
diff --git a/generator/src/main/resources/base/io/apicurio/umg/base/MappedNode.java b/generator/src/main/resources/base/io/apicurio/umg/base/MappedNode.java
index 414a69c..4733b3d 100644
--- a/generator/src/main/resources/base/io/apicurio/umg/base/MappedNode.java
+++ b/generator/src/main/resources/base/io/apicurio/umg/base/MappedNode.java
@@ -29,6 +29,15 @@ public interface MappedNode<T> {
      */
     public void addItem(String name, T item);
 
+    /**
+     * Inserts a child item.
+     *
+     * @param name
+     * @param item
+     * @param atIndex
+     */
+    public void insertItem(String name, T item, int atIndex);
+
     /**
      * Removes a child item by name and returns the deleted child or undefined if there wasn't one.
      * 
diff --git a/generator/src/main/resources/base/io/apicurio/umg/base/util/DataModelUtil.java b/generator/src/main/resources/base/io/apicurio/umg/base/util/DataModelUtil.java
new file mode 100644
index 0000000..98b5893
--- /dev/null
+++ b/generator/src/main/resources/base/io/apicurio/umg/base/util/DataModelUtil.java
@@ -0,0 +1,46 @@
+package io.apicurio.umg.base.util;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public class DataModelUtil {
+
+    public static <V> Map<String, V> insertMapEntry(Map<String, V> map, String key, V value, int atIndex) {
+        // If the new key is present, then return without modification.
+        if (map.containsKey(key)) {
+            return map;
+        }
+        // If the map isn't an LHM then ordering can't be maintained anyway
+        // If the atIndex is null then we're trying to undo a command that was persisted prior to this functionality being added
+        // If the atIndex is >= the map size it has to go at the end anyway
+        if (!(map instanceof LinkedHashMap) || atIndex >= map.size()){
+            map.put(key, value);
+            return map;
+        }
+
+        final LinkedHashMap<String, V> newMap = new LinkedHashMap<>();
+        // In order to maintain ordering of the elements when replacing a key in a LinkedHashMap,
+        // create a new instance and populate it in insertion order
+        int index = 0;
+        for (Map.Entry<String, V> entry : map.entrySet()) {
+            if (index++ == atIndex) {
+                newMap.put(key, value);
+            }
+            newMap.put(entry.getKey(), entry.getValue());
+        }
+        return newMap;
+    }
+
+    public static <V> List<V> insertListEntry(List<V> list, V value, int atIndex) {
+        if (atIndex >= list.size()) {
+            list.add(value);
+        } else if (atIndex < 0) {
+            list.add(0, value);
+        } else {
+            list.add(atIndex, value);
+        }
+        return list;
+    }
+
+}
diff --git a/generator/src/test/java/io/apicurio/umg/GeneratorTest.java b/generator/src/test/java/io/apicurio/umg/GeneratorTest.java
new file mode 100644
index 0000000..5d2722d
--- /dev/null
+++ b/generator/src/test/java/io/apicurio/umg/GeneratorTest.java
@@ -0,0 +1,50 @@
+package io.apicurio.umg;
+
+import io.apicurio.umg.io.SpecificationLoader;
+import io.apicurio.umg.models.spec.SpecificationModel;
+import org.apache.commons.io.FileUtils;
+import org.junit.Test;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.util.List;
+
+public class GeneratorTest {
+
+    @Test
+    public void testGenerator() throws Exception {
+        File outputDir;
+
+        String outputDirPath = System.getenv("GENERATE_TEST_OUTPUT_DIR");
+        if (outputDirPath != null) {
+            outputDir = new File(outputDirPath);
+            outputDir.mkdirs();
+        } else {
+            outputDir = Files.createTempDirectory(GeneratorTest.class.getSimpleName()).toFile();
+        }
+
+        File umgTestOutputDir = Files.createTempDirectory(GeneratorTest.class.getSimpleName() + "-test").toFile();
+        UnifiedModelGeneratorConfig config = UnifiedModelGeneratorConfig.builder()
+                .outputDirectory(outputDir)
+                .testOutputDirectory(umgTestOutputDir)
+                .generateTestFixtures(false)
+                .rootNamespace("io.apicurio.umg.test").build();
+        // Load the specs
+        List<SpecificationModel> specs = List.of(
+                SpecificationLoader.loadSpec(GeneratorTest.class.getResource("openapi.yaml"))
+        );
+        // Create a unified model generator
+        UnifiedModelGenerator generator = new UnifiedModelGenerator(config, specs);
+        // Generate the source code into the target output directory.
+        try {
+            generator.generate();
+        } finally {
+            if (outputDirPath == null) {
+                FileUtils.deleteDirectory(outputDir);
+                FileUtils.deleteDirectory(umgTestOutputDir);
+            }
+        }
+
+    }
+
+}
\ No newline at end of file
diff --git a/generator/src/test/resources/io/apicurio/umg/openapi-3.0.yaml b/generator/src/test/resources/io/apicurio/umg/openapi-3.0.yaml
new file mode 100644
index 0000000..2ad4d84
--- /dev/null
+++ b/generator/src/test/resources/io/apicurio/umg/openapi-3.0.yaml
@@ -0,0 +1,626 @@
+name: OpenAPI 3.0
+version: 3.0
+versions:
+  - version: 3.0.0
+    url: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md
+  - version: 3.0.1
+    url: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md
+  - version: 3.0.2
+    url: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md
+  - version: 3.0.3
+    url: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md
+prefix: OpenApi30
+namespace: io.apicurio.umg.test.v30
+
+traits:
+  - name: Extensible
+    properties:
+      - name: '/^x-.+$/'
+        type: any
+        collection: extensions
+  - name: Referenceable
+    properties:
+      - name: '$ref'
+        type: string
+
+entities:
+  - name: Document
+    root: true
+    traits:
+      - Extensible
+    properties:
+      - name: openapi
+        type: string
+      - name: info
+        type: Info
+      - name: servers
+        type: '[Server]'
+      - name: paths
+        type: Paths
+      - name: components
+        type: Components
+      - name: security
+        type: '[SecurityRequirement]'
+      - name: tags
+        type: '[Tag]'
+      - name: externalDocs
+        type: ExternalDocumentation
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Info
+    traits:
+      - Extensible
+    properties:
+      - name: title
+        type: string
+      - name: description
+        type: string
+      - name: termsOfService
+        type: string
+      - name: contact
+        type: Contact
+      - name: license
+        type: License
+      - name: version
+        type: string
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Contact
+    traits:
+      - Extensible
+    properties:
+      - name: name
+        type: string
+      - name: url
+        type: string
+      - name: email
+        type: string
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: License
+    traits:
+      - Extensible
+    properties:
+      - name: name
+        type: string
+      - name: url
+        type: string
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Server
+    traits:
+      - Extensible
+    properties:
+      - name: url
+        type: string
+      - name: description
+        type: string
+      - name: variables
+        type: '{ServerVariable}'
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: ServerVariable
+    traits:
+      - Extensible
+    properties:
+      - name: enum
+        type: '[string]'
+      - name: default
+        type: string
+      - name: description
+        type: string
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Components
+    traits:
+      - Extensible
+    properties:
+      - name: schemas
+        type: '{Schema}'
+      - name: responses
+        type: '{Response}'
+      - name: parameters
+        type: '{Parameter}'
+      - name: examples
+        type: '{Example}'
+      - name: requestBodies
+        type: '{RequestBody}'
+      - name: headers
+        type: '{Header}'
+      - name: securitySchemes
+        type: '{SecurityScheme}'
+      - name: links
+        type: '{Link}'
+      - name: callbacks
+        type: '{Callback}'
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Paths
+    traits:
+      - Extensible
+    properties:
+      - name: '*'
+        type: PathItem
+    propertyOrder:
+      - $Extensible
+      - $this
+
+  - name: PathItem
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: summary
+        type: string
+      - name: description
+        type: string
+      - name: get
+        type: Operation
+      - name: put
+        type: Operation
+      - name: post
+        type: Operation
+      - name: delete
+        type: Operation
+      - name: options
+        type: Operation
+      - name: head
+        type: Operation
+      - name: patch
+        type: Operation
+      - name: trace
+        type: Operation
+      - name: servers
+        type: '[Server]'
+      - name: parameters
+        type: '[Parameter]'
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Operation
+    traits:
+      - Extensible
+    properties:
+      - name: tags
+        type: '[string]'
+      - name: summary
+        type: string
+      - name: description
+        type: string
+      - name: externalDocs
+        type: ExternalDocumentation
+      - name: operationId
+        type: string
+      - name: parameters
+        type: '[Parameter]'
+      - name: requestBody
+        type: RequestBody
+      - name: responses
+        type: Responses
+      - name: callbacks
+        type: '{Callback}'
+      - name: deprecated
+        type: boolean
+      - name: security
+        type: '[SecurityRequirement]'
+      - name: servers
+        type: '[Server]'
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: ExternalDocumentation
+    traits:
+      - Extensible
+    properties:
+      - name: description
+        type: string
+      - name: url
+        type: string
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Parameter
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: name
+        type: string
+      - name: in
+        type: string
+      - name: description
+        type: string
+      - name: required
+        type: boolean
+      - name: deprecated
+        type: boolean
+      - name: allowEmptyValue
+        type: boolean
+      - name: style
+        type: string
+      - name: explode
+        type: boolean
+      - name: allowReserved
+        type: boolean
+      - name: schema
+        type: Schema
+      - name: example
+        type: any
+      - name: examples
+        type: '{Example}'
+      - name: content
+        type: '{MediaType}'
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: RequestBody
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: description
+        type: string
+      - name: content
+        type: '{MediaType}'
+      - name: required
+        type: boolean
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: MediaType
+    traits:
+      - Extensible
+    properties:
+      - name: schema
+        type: Schema
+      - name: example
+        type: any
+      - name: examples
+        type: '{Example}'
+      - name: encoding
+        type: '{Encoding}'
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Encoding
+    traits:
+      - Extensible
+    properties:
+      - name: contentType
+        type: string
+      - name: headers
+        type: '{Header}'
+      - name: style
+        type: string
+      - name: explode
+        type: boolean
+      - name: allowReserved
+        type: boolean
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Responses
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: default
+        type: Response
+      - name: '*'
+        type: Response
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Response
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: description
+        type: string
+      - name: headers
+        type: '{Header}'
+      - name: content
+        type: '{MediaType}'
+      - name: links
+        type: '{Link}'
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Callback
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: '*'
+        type: PathItem
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Example
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: summary
+        type: string
+      - name: description
+        type: string
+      - name: value
+        type: any
+      - name: externalValue
+        type: string
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Link
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: operationRef
+        type: string
+      - name: operationId
+        type: string
+      - name: parameters
+        type: '{any}' # TODO {any|expression}
+      - name: requestBody
+        type: any # TODO any|expression
+      - name: description
+        type: string
+      - name: server
+        type: Server
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Header
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: description
+        type: string
+      - name: required
+        type: boolean
+      - name: deprecated
+        type: boolean
+      - name: allowEmptyValue
+        type: boolean
+      - name: style
+        type: string
+      - name: explode
+        type: boolean
+      - name: allowReserved
+        type: boolean
+      - name: schema
+        type: Schema
+      - name: example
+        type: any
+      - name: examples
+        type: '{Example}'
+      - name: content
+        type: '{MediaType}'
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Tag
+    traits:
+      - Extensible
+    properties:
+      - name: name
+        type: string
+      - name: description
+        type: string
+      - name: externalDocs
+        type: ExternalDocumentation
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: Schema
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: format
+        type: string
+      - name: title
+        type: string
+      - name: description
+        type: string
+      - name: default
+        type: any
+      - name: multipleOf
+        type: number
+      - name: maximum
+        type: number
+      - name: exclusiveMaximum
+        type: boolean
+      - name: minimum
+        type: number
+      - name: exclusiveMinimum
+        type: boolean
+      - name: maxLength
+        type: integer
+      - name: minLength
+        type: integer
+      - name: pattern
+        type: string
+      - name: maxItems
+        type: integer
+      - name: minItems
+        type: integer
+      - name: uniqueItems
+        type: boolean
+      - name: maxProperties
+        type: integer
+      - name: minProperties
+        type: integer
+      - name: required
+        type: '[string]'
+      - name: enum
+        type: '[any]'
+      - name: type
+        type: string
+      - name: items
+        type: Schema
+      - name: allOf
+        type: '[Schema]'
+      - name: properties
+        type: '{Schema}'
+      - name: additionalProperties
+        type: 'boolean|Schema'
+      - name: readOnly
+        type: boolean
+      - name: xml
+        type: XML
+      - name: externalDocs
+        type: ExternalDocumentation
+      - name: example
+        type: any
+      - name: oneOf
+        type: '[Schema]'
+      - name: anyOf
+        type: '[Schema]'
+      - name: not
+        type: Schema
+      - name: discriminator
+        type: Discriminator
+      - name: nullable
+        type: boolean
+      - name: writeOnly
+        type: boolean
+      - name: deprecated
+        type: boolean
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: Discriminator
+    properties:
+      - name: propertyName
+        type: string
+      - name: mapping
+        type: '{string}'
+    propertyOrder:
+      - $this
+
+  - name: XML
+    traits:
+      - Extensible
+    properties:
+      - name: name
+        type: string
+      - name: namespace
+        type: string
+      - name: prefix
+        type: string
+      - name: attribute
+        type: boolean
+      - name: wrapped
+        type: boolean
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: SecurityScheme
+    traits:
+      - Extensible
+      - Referenceable
+    properties:
+      - name: type
+        type: string
+      - name: description
+        type: string
+      - name: name
+        type: string
+      - name: in
+        type: string
+      - name: scheme
+        type: string
+      - name: bearerFormat
+        type: string
+      - name: flows
+        type: OAuthFlows
+      - name: openIdConnectUrl
+        type: string
+    propertyOrder:
+      - $Referenceable
+      - $this
+      - $Extensible
+
+  - name: OAuthFlows
+    traits:
+      - Extensible
+    properties:
+      - name: implicit
+        type: OAuthFlow
+      - name: password
+        type: OAuthFlow
+      - name: clientCredentials
+        type: OAuthFlow
+      - name: authorizationCode
+        type: OAuthFlow
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: OAuthFlow
+    traits:
+      - Extensible
+    properties:
+      - name: authorizationUrl
+        type: string
+      - name: tokenUrl
+        type: string
+      - name: refreshUrl
+        type: string
+      - name: scopes
+        type: '{string}'
+    propertyOrder:
+      - $this
+      - $Extensible
+
+  - name: SecurityRequirement
+    properties:
+      - name: '*'
+        type: '[string]'
+    propertyOrder:
+      - $this
diff --git a/generator/src/test/resources/io/apicurio/umg/openapi.yaml b/generator/src/test/resources/io/apicurio/umg/openapi.yaml
new file mode 100755
index 0000000..1a644fe
--- /dev/null
+++ b/generator/src/test/resources/io/apicurio/umg/openapi.yaml
@@ -0,0 +1,7 @@
+name: OpenAPI
+url: https://www.openapis.org/
+description: The OpenAPI Specification allows the description of a remote API accessible through HTTP or HTTP-like protocols.
+prefix: OpenApi
+namespace: io.apicurio.umg.test
+versions:
+  - $ref: ./openapi-3.0.yaml